For some years filters have been made having an external casing and an upper closing cover, which define an internal chamber having an inlet for the liquid to be filtered and an outlet for the filtered liquid, and a filter cartridge having a tubular filter means, located internally of the internal chamber, which separates the chamber into a first zone communicating with the inlet and a second zone communicating with the outlet.
The filter cartridge is constrained to the upper cover by means of an upper plate joined to the upper end of the filter means and, when it is worn out and needs to be replaced, is separated from the cover and replaced with a new cartridge.
The filters are favoured at present because there is no need to dispose of and destroy the whole filter but only the worn-out filter cartridge.
The accessibility of the cartridge is also facilitated by the fact that as it is constrained to the closing cover of the casing, when the casing is opened the cartridge follows the cover, exiting from the fluid it is immersed in without there being any need to access it with tools and without any need to shake it or unblock it, causing dirt to detach from it, which is always damaging.
To constrain the cartridge and the cover to one another, it is known to realise first hooking elements and second hooking agents to realise a reciprocal snap-fastening, where the first hooking elements (or the second hooking elements) are joined to the cover and project axially towards the inside of the chamber and, vice versa, the second hooking elements (or the first hooking elements) are joined to the upper plate and project axially towards the upper cover.
A drawback connected to these filters is that since the used filter cartridge, impregnated with liquid, is attached to the cover, when the external casing is removed, separating it from the cover, the liquid drips from the cartridge, fouling not only the operator but also the surrounding environment and parts of the engine.
The aim of the present patent is to obviate the above-described drawback.
Disclosure of Invention
The aim is attained by a filter having the characteristics recited in claim 1.
Primarily the objective is attained by making the cartridge removably fastened to the casing such as to remain internally of the casing when the casing is separated from the cover.
The invention further comprises advantageous means for removably fastening the cartridge to the bottom of the cover, such as to facilitate the engaging/disengaging rapidly and securely.
The invention is based on the fact that it comprises first hooking elements which are solidly constrained to the casing and exhibiting hooking teeth, developing axially and having an elastic action in a radial direction, and second hooking elements which are solidly constrained to the cartridge, which have a generally cylindrical surface that is subdivided into a number of equal sectors which is equal to the hooking teeth, where each sector defines a hooking zone for axially constraining the hooking teeth in a snap-fastening arrangement, and a disengaging zone, located by a side of the hooking zone, destined to free the hooking teeth from the constraint with the hooking zone following a rotation, over a limited angle, of the cartridge with respect to the casing.